Power-wrench control system



April 1968 F. J. HILLMAN 3,380,324

POWER-WRENCH CONTROL SYSTEM Filed April 18, 1966 3 Sheets-Sheet 1 1122915, J K/Ear, Bus-554.4 #745? A ril 30, 1968 F. J. HILLMAN POWER-WRENCH CONTROL SYSTEM 3 Sheets-Sheet Filed April 18, 1966 INVENTGR. CI. 11744 MAM F 4 2 M iw WM w w m f a m .9 i e A 4 ii: IWiIJ Q. 6 3 W.

mmeacwqq United States Patent 3,380,324 POWER-WRENCH CONTROL SYSTEM Fred J. Hillman, Long Beach, Calif., assignor to Hillman- Kelley, Los Angeles, Calif., a partnership Filed Apr. 18, 1966, Ser. No. 543,280 Claims. (Cl. 81-54) ABSTRACT OF THE DISCLOSURE A control system for a power wrench which includes a housing, a jaw-carrying rotor rotatable in opposite directions, a reversible motor for rotating the rotor in opposite directions, and motor actuating means selectively movable from a neutral position into two operating positions for selectively energizing the motor for rotation in opposite directions, the motor actuating means being biased toward its neutral position. The control system includes a manually-operable control for selectively moving the motor actuating means from its neutral position into its operating positions, a releasable latch for selectively latching the motor actuating means in one of its operating positions to prevent it from returning to its neutral position, and mechanism for releasing the latch as the rotor approaches a predetermined angular position relative to the housing so that the motor actuating means returns to its neutral position to deenergize the motor.

Background of invention The present invention relates in general to power tongs or wrenches and, more particularly, to a power wrench which is especially suitable for making or breaking threaded joints in pipe or rod strings when running such strings into or out of oil wells, for example.

As background, the invention contemplates a power Wrench of the type which includes a housing, an annular rotor carried by and rotatable relative to the housing, jaws carried by the rotor and closable on a pipe, rod, or the like, within the rotor, means for closing and opening the jaws, a reversible motor carried by the housing and connected to the rotor for rotating the rotor in opposite directions, and motor actuating means on the housing and selectively movable from a neutral position into two operating positions for selectively energizing the motor for rotation in opposite directions, the motor actuating means being biased toward its neutral position. In a power wrench of this type, it is necessary to rotate the rotor into a predetermined angular position relative to the housing in order to engage the wrench with, or disengage it from, one component of a threaded joint to be made up or broken. For example, the housing and the rotor may be provided with registrable radial throats permitting radial insertion and withdrawal of a pipe or rod string, it being necessary to rotate the rotor into a position wherein the radial throat therein registers with the radial throat in the housing to permit engagement of the power wrench with and disengagement thereof from the pipe or rod string. As a matter of convenience, the invention will be considered herein in connection with a power wrench having the foregoing characteristics, it being understood, however, that the invention is applicable to any power wrench having a rotor which must be rotated into a predetermined angular position relative to a housing for application to and disengagement from a threaded joint to be made up or broken.

Summary and objects of invention The primary object of the present invention is to provide an improved control system for a power wrench of the foregoing type which is capable of placing the rotor "ice in the desired angular position relative to the housing quickly and accurately in order to permit application of the power wrench to or disengagement thereof from the threaded joint to be made up or broken.

Another and important object is to provide a control system capable of rotating the rotor into the desired angular position relative to the housing in either direction selectively, depending upon whether the rotor is being rotated into the desired angular position after making up or breaking a threaded joint. As will be explained hereinafter, it is necessary to rotate the rotor into the desired angular position in one direction after making up a threaded joint, and to rotate the rotor into the desired angular position in the opposite direction after breaking a threaded joint. The selective control system of the invention is capable of achieving this, which is an important feature.

Still another important object of the invention is to provide a selective control system of the foregoing nature having manually-operable control means capable of producing rotor rotation in one direction in making up or breaking a threaded joint, and capable of producing rotor rotation in the opposite direction in order to place the rotor in the desired angular position permitting disengagement of the power wrench from the threaded joint.

More specifically, objects of the invention are to provide a power-wrench control system. which includes: manually-operable control means on the housing for selectively moving the motor actuating means from its neutral position into its operating positions; latch means on the housing for selectively latching the motor actuating means in one of its operating positions; and interengageable means on the housing and the rotor for releasing the latch means as the rotor approaches a predetermined angular position relative to the housing.

A further object is to provide a power-Wrench control system of the foregoing nature wherein the latch means mentioned includes: a first latch element; a second latch element having two engagement means selectively engageable by the first latch element to latch the motor actuating means in its respective operating positions; and selector means for selectively preventing engagement of the first latch element with one of the engagement means.

Still another object is to provide a power-wrench control system wherein: the control means includes a control shaft mounted on the housing for selective pivotal movement from a neutral position into two operating positions respectively corresponding to the neutral position and the two operating positions of the motor actuating means; the motor actuating means is connected to the control shaft; the first latch element is connected to the interengageable means; and the second latch element is mounted on and connected to the control shaft.

Yet another object is to provide means for angularly adjusting the position of the second latch element relative to the control shaft to adjust the speed of the motor when the motor actuating means is latched in either of its operating positions.

Yet another object is to provide a power-wrench control system wherein the interengageable means on the housing and the rotor, for releasing the latch means as the rotor approaches a predetermined angular position relative to the housing, includes a cam on the rotor and means on the housing and engageable by the cam for releasing the latch means as the rotor approaches the desired predetermined angular position.

An additional object of the invention is to provide a power-wrench control system wherein the manuallyoperable control means includes a control lever between and generally parallel to two hand grips on the housing, the control lever and one of the hand grips being graspable to produce rotor rotation in one direction, and the control lever and the other hand grip being graspable to produce rotor rotation in the opposite direction.

The foregoing objects, advantages, features and results of the present invention, together with various other objects, advantages, features and results thereof which will be evident to those skilled in the power wrench art in the light of this disclosure, may be achieved with the exemplary embodiment of the invention described in detail hereinafter and illustrated in the accompanying drawings.

Description of drawings In the drawings:

FIG. 1 is a perspective view of an apparatus for making up or breaking threaded joints in pipe or rod strings when running such strings into or out of oil wells, for example, which apparatus includes the power wrench control system of the invention; 7

FIG. 2 is an enlarged, fragmentary, horizontal sectional view taken as indicated by the arrowed line 22 of FIG. 1;

FIG. 3 is an enlarged, fragmentary, vertical sectional view taken as indicated by the arrowed line 3-3 of FIG. 2;

FIGS. 4 and 5 are views similar to FIG. 3, but showing other operating positions of the various parts; and

FIG. 6 is a sectional view taken as indicated by the arrowed line 66 of FIG. 3.

Description of preferred embodiment of invention Referring initially to FIG. 1 of the drawings, illustrated therein is an apparatus 2%} for making or breaking threaded joints in pipe or rod strings, such as a threaded joint 22 in a drill string 24. The entire apparatus 20 is shown as suspended from a hook 26 at the lower end of a cable, not shown, so that it may be swung laterally into and out of engagement with the drill string 24.

More particularly, the apparatus 20 includes a vertical post 28 shown as having at its upper end and eye 30 engageable with the hook 26. A power tong or wrench which embodies the invention is designated generally by the numeral 32 and is suitably carried by the post 28. As will become apparent, the power wrench 32 is designed to be engaged with or disengaged from an upper section 34- of the drill string 24 by swinging it to the left or right, as viewed in FIG. 1 of the drawings. It will be noted that, in the particular construction illustrated, the power wrench 32 is intended to engage the upper drill-string section 34 above the threaded joint 22 between the upper section 34 and a lower section 36. The threaded joint 22 may be of the usual pin and box type, the pin being formed at the lower end of the upper section 34 and the box being formed at the upper end of the lower section 36.

The apparatus 20 is also shown as including a back-up tong or wrench 38 engageable with the box at the upper end of the lower drill-string section 36 to prevent rotation thereof while making or breaking the joint 22. The back-up wrench 38, which is more fully described and claimed in the co-pending patent application of Andrew B. Campbell, Ser. No. 543,329, filed Apr. 18, 1966, and assigned to the same assignee as this application, is pivotable about a subpost 40 into and out of engagement with the box at the upper end of the lower drill-string section 36, after the power wrench 32 has been swung laterally into engagement with the upper drill-string section 34. The subpost 40 is telescoped upwardly into a depending socket 41 on the power wrench 32 and is detachably connected thereto by a suitable connector 42. The back-up wrench 38 is supported on the subpost 40 by a compression spring 44 seated on a removable pin 46. By removing the pin 46 and the spring 44, the back-up wrench 38 may be slipped downwardly elf the lower end of the subpost 40 so that it can be turned over and reinstalled on the subpost upside down relative to the position shown in FIG. 1 of the drawings. With this construction, the position of the back-up wrench 38 on the subpost 40 can be reversed readily when switching from making threaded joints to breaking them, or vice versa. The back-up wrench 38 per se forms no part of the present invention, and since it is fully disclosed in the aforementioned co-pending application, it will not be described further herein.

The power wrench 32 per se also forms no part of the present invention. The power wrench 32 is fully disclosed and claimed in the co-pending patent application of Andrew B. Campbell, Ser. No. 527,720, filed Feb. 15, 1966, and assigned to the same asignee as the present application. Consequently, the power wrench 32 will be described herein only to the extent necessary for a complete disclosure of the power-wrench control system of the present invention.

Considering the power wrench 32 briefly with reference to FIGS. 1 and 2 of the drawings, it includes a housing 50 carried by the post 28 and carrying the depending socket 41, these elements preferably being axially aligned. The housing 50 is provided with a radial throat 52 for lateral application of the power wrench 32 to and lateral disengagement thereof from the upper drill-string section 34. The outer end of the radial throat 52 is normally closed by two pivoted, spring-biased guards 54 which open and close automatically as the power wrench 32 is applied to and disengaged from the drill string 24.

Rotatable in the housing 50 about a rotor axis paralleling the axis of the post 28 is an annular rotor 56 having a radial throat 58 registrable with the radial throat 52, as shown in FIG. 2, when the power wrench 32 is to be applied to or disengaged from the drill string 24. The rotor 56 carries a jaw assembly 60 having a radial throat 62 registrable with the throats 52 and 58 in the housing 50 and rotor 56. The jaw assembly 60 is adapted to close on the drill-string section 34 upon limited rotation of the rotor 56 relative to the jaw assembly in either direction so that the power wrench 32 can be used to screw the pin at the lower end of the upper section 34 into the box at the upper end of the lower section 36, or to unscrew it therefrom. Consequently, the power wrench 32 may be used for making or breaking the threaded joint 22 merely by reversing the direction of rotation of the rotor 56. However, the power wrench 32 is provided with means for preventing closing of the jaw assembly 60 upon rotation of the rotor 56 in either direction. Thus, after making or breaking the threaded joint 22, the direction of rotation of the rotor 56 can be reversed, without closing the jaw assembly 60, to permit registering of the radial throats 56 and 62 in the rotor and the jaw assembly with the radial throat 52 in the housing 50, without reversing the previously-completed joint making or breaking operation. These aspects of the power wrench 32 are fully disclosed in the aforementioned co-pending Campbell application Ser. No. 527,720 so that no further description herein is necessary.

Considering the manner in which the rotor 56 is driven in either direction, the power wrench 32 includes a reversible motor 64 mounted on the housing 50, this motor being shown as a fluid motor, specifically a hydraulic motor, having flexible supply and return lines 66 and 68 connected thereto. The motor 64 is controlled by a motor actuating means 70 comprising an open-center valve selectively movable from an intermediate neutral position into two operating positions to selectively energize the motor in opposite directions of rotation, the open-center valve being spring biased into its central neutral position so that it automatically returns thereto. Reversible hydraulic motors with actuating valves of this type are well known in the art so that a further description herein is not required.

The reversible hydraulic motor 64 is suitably connected to one end of a gear train 72, FIG. 2, the other end of which is meshed with a gear 74 on the rotor 56 to drive the rotor in either direction, depending upon the direction of rotation of the motor. If desired, the gear train 72 may include speed-changing gears, not shown, to permit the rotor 56 to be driven in either direction at difierent speeds. Such speed-changing gears may be controlled by a gear shifting lever 76, FIG. 1, connected to the outer end of a gear shifting shaft 78. The housing 50 is provided on opposite sides of the radial throat 52 therein with hand grip members 80 and 82, and the latter has an auxiliary gear shifting lever 84 pivotally connected thereto. The auxiliary gear shifting lever 84 is suitably connected to the gear shifting shaft 78 by a link 86, in a manner not specifically shown. Thus, the speed changing gears in the gear train 72 may be shifted by means of either the lever 76, or the lever 84.

Structure of control system 90 Turning now to the power-wrench control system of the invention, it is designated generally in FIG. 1 of the drawings by the numeral 90 and performs two principal functions. First, it controls the direction of rotation of the reversible hydraulic motor 64, and thus the direction of rotation of the rotor 56. Second, during reversed rotation of the motor 64 after making or breaking the threaded joint 22, the control system 90 stops the rotor with the throats 58 and 62 in the rotor and the jaw assembly 60 in register with the throat 52 in the housing 50, so that the power wrench 32 may be disengaged from the drill string 24.

The control system 90 includes a transverse control shaft 92 pivotally mounted on the housing 50 of the power wrench 32 intermediate the rotor 56 and the reversible hydraulic motor 64. Fixed on the control shaft 92 intermediate its end is an arm 94, FIGS. 2 to 5, pivotally connected to one end of a link 96. The other end of this link is pivotally connected to an actuating arm 98 of the motor actuating means or valve 70. When the control shaft 92 and the control arm 94 thereon are in the positions shown in FIG. 3 of the drawings, the motor actuating valve 70 is in its neutral position so that the motor 64 is not energized. When the control arm 94 is in the position of FIG. 4, the motor actuating valve 70 is displaced from its neutral position toward one of its operating positions to cause the reversible motor 64 to drive the rotor 56 in one direction. Conversely, when the control arm 94 is in the position of FIG. 5, it displaces the motor actuating valve 70 from its neutral position toward its other operating position to cause the reversible motor 64 to drive the rotor 56 in the opposite direction. It will be assumed for convenience that when the control arm 94 is in the FIG. 4 position, the rotor 56 rotates in the clockwise direction, and that when the control arm is in the FIG. 5 position, the rotor rotates in the counterclockwise direction.

The control arm 94 is biased into its neutral position, FIG. 3, by the hereinbefore-discussed biasing means which biases the motor actuating valve 70 into its neutral position. The control arm 94 is pivoted from its neutral position into its clockwise operating position, FIG. 4, or its counterclockwise operating position, FIG. 5, by a generally vertical control lever 100 pivotally mounted at its upper end on the hand grip member 80. One end of a link 102 is pivotally connected to the lower end of the control lever 100, and the other end of this link is pivotally connected to a control arm 104 fixed on the outer end of the control shaft 92. The hand grip member 80 includes two generally vertical hand grips 106 and 108 on opposite sides of the control lever 100. By grasping the control lever 100 and the hand grip 106, the control lever may be pushed toward the hand grip 106 to pivot the control arm 94 into the FIG. 4 position, thereby producing clockwise rotation of the rotor 56 under the hereinbefore-assumed conditions. Conversely, by grasping the control lever 100 and the hand grip 108, the control lever may be pulled toward the hand grip 108 to pivot the control arm 94 into the FIG. 5 position, thereby producing counterclockwise rotation of the rotor 56 under the assumed conditions. When the control lever 100 is released, it is returned to its neutral position, FIG. 1, by the biasing means incorporated in the motor actuating valve 70.

The control system includes latch means for selectively latching the motor actuating valve 70 in one of its operating positions, and includes interengageable means 112 on the housing 50 and the rotor 56 for releasing the latch means as the rotor approaches an angular position wherein the throat 58 in the rotor is in register with the throat 52 in the housing. When the latch means 110 is released in this manner, the motor actuating valve 70 returns to its neutral position to de-energize the motor 64. The interengageable means 112 releases the latch means 110 at an angular position of the rotor 56 such that the rotor will coast into the desired throat-registering position. As will be discussed hereinafter, the angular extent of rotor coasting after de-energization of the motor 64 may be adjusted to obtain extremely accurate registering of the throat 58 in the rotor with the throat 52in the housing 50.

Considering the latch means 110 in more detail, it includes a latch element 114 pivotally mounted on the outer end of the control shaft 92. The latch element 114 is provided with an arm 116 which projects between oppositely-facing adjusting screws 118 respectively carried by arms 120 of a yoke 122 fixed on the control shaft 92. As will be apparent, the relative angular positions of the latch element 114 and the yoke 122 can be varied by means of the adjusting screws 118. This adjustment varies the angular position of the control arm 94 corresponding to the angular position in which the latch element 114 is releasably secured by the latch means 110. Consequently, this adjustment varies the speed at which the motor 64 rotates when the latching element 114 is releasably secured by the latch means 110. Thus, the adjustment of the angular position of the latch element 114 which is provided by the adjusting screws 118 varies the angular extent to which the rotor 56 will coast upon releasing the latch means 110. The ultimate result, therefore, is to obtain accurate registering of the throat 58 in the rotor 56 with the throat 52in the housing 50, which is an important feature of the invention.

In addition to the latch element 114, the latch means 110 includes a latch element 124 actuable by the interengageable means 112. More particularly, the latch element 124 is engagea'ble with either of two engagement means on the latch element 114 to releasably retain the latter in positions to produce throat-registering rotation of the rotor 56 in opposite directions. The latch element 124 is shown as having the form of a pawl insertable into either of two notches 126 and 128 in the latch element 114. Insertion of the pawl 124 into the notch 126 latches the motor actuating valve 70 in a position to produce throat-registering rotation of the rotor 56 in the counterclockwise direction, while insertion of the pawl into the notch 128 latches the motor actuating valve in a position to produce clockwise throat-registering rotation of the rotor 56. The notches 126 and 128 are selectively operable, as will be described in the next paragraph, so that the motor actuating valve 70 can be latched in a position to produce either clockwise or counterclockwise throatregistering rotation of the rotor 56, but not both.

Pivotally mounted on the control shaft 92 is a selector means or element 130 capable of closing or covering one or the other of the notches 126 and 128 in the latch element 114. The selector element 130 is provided with an actuating handle 132 for shifting it between a position wherein it covers the notch 126 and a position wherein it covers the notch 128. The selector element 130 is releasably held in its two angular positions relative to the latch element 114 by a detent 134 on the latch element insertable into either of two detent recesses 136 in the selector element, as best shown in FIG. 6. The detent 134 is formed by a rib on a leaf spring 138 secured to the latch element 114 on opposite sides of the selector element 130 by screws 140. These screws also act as stops to limit angular displacement of the selector element 130 relative to the latch element 114.

Thus, with the foregoing construction, either the notch 126 or the notch 128 is blocked out by the selector element 130, the selector element being shown in FIGS. 3 to 5 of the drawings as in a position to block out the notch 128. Consequently, the latch means 110 is inoperative when the control system 90 is operated to produce clockwise rotation of the rotor 56, the latch means being operative only when the control system is in a position to produce counterclockwise rotor rotation. This corresponds to the situation wherein the power wrench 32 is used to make the threaded joint 22, the direction of rotation of the rotor 56 subsequently being reversed to register the throat 58 in the rotor with the throat 52 in the housing 50. During such reversed rotation for throat-registering purposes, the latch means 110 is operative. In the event that it is desired to achieve throat registering after breaking of the joint 22, the latch means 110 can be rendered operative for this purpose by shifting the selector element 130 into a position to block out the notch 126, instead of the notch 128. Thus, the selector element 130 permits the latch means 110 to be used selectively to achieve accurate throat registering during reversed rota tion of the rotor 56 in either direction, which is an important feature of the invention.

It will be noted that the notches 126 and 128 in the latch element 114 are somewhat wider than the end of the .pawl 124 insertable thereinto. This permits some manual overriding of the throat-registering speed for which the latch means 110 is adjusted. For example, if the control lever 100 is manipulated to cause the pawl 124 to engage the opposite side of the notch 126 from that shown as engaged thereby in FIG. 5, the speed of rotation of the rotor 56 will be increased slightly. This is desirable in overcoming starting friction, for example, in initiating counterclockwise rotor rotation. If the control lever 100 is subsequently released, the parts will assume the relative positions shown in FIG. 5 to permit continued counterclockwise rotation of the rotor 56 at the throatregistering speed for which the adjusting screws 118 are set.

The pawl 124 is pivotally mounted on a shaft 142 carried by the housing 50 and paralleling the control shaft 92. The interengageable means 112 for releasing the latch means 110 includes an arm 144 pivotally mounted on the shaft 142 and rigidly connected to the pawl 124 in any suitable manner, as by welding. The arm 144 and the pawl 124 are biased toward the positions shown in FIG. 5 by a tension spring 146 connected at one end to the arm 144 and at its other end to the housing 50.

The free end of the arm 144 engages the outer end of a push rod 148, FIGS. 2 to 5, which is oriented generally radially of the rotor 56 and which is radially slidable in suitable bearings 150 on the housing 50. The push rod 148 is biased outwardly by a compression spring 152 thereon, the spring 146 being capable of overriding the spring 152 when the parts are in the positions shown in FIG. 5. The inner end of the push rod 148 is engageable by a cam 154, FIG. 2, on the rotor 56. This cam is so located circumferentially of the rotor 56 that it engages the push rod 148 to release the latch means 110 as the throat 58 in the rotor approaches register with the throat 52 in the housing 50. Since releasing of the latch means 110 results in de-energization of the motor 64, as previously explained, the rotor 56 coasts to a stop as the throat 58 therein registers with the throat 52. As previously pointed out, exact register is attained by controlling the angular extent of rotor coasting through adjustment of the throat-registering speed of the rotor 56 by means of the adjusting screws 118.

Operation of control system 90 In considering the operation of the invention, it will be assumed that the power wrench 32 is to be used to make the threaded joint 22 by driving the rotor 56 in the clockwise direction, and that the direction of rotor rotation is subsequently to be reversed to align the throat 58 in the rotor with the throat 52 in the housing so that the power wrench can be disengaged from the drill string 24. For this mode of operation, the selector element 130 is set in an angular position relative to the latch element 114 to block out the notch 128 in the latch element. (It will be understood that the mode of operation during throat registering after breaking the threaded joint 22 is similar, but reversed, the selector element 130 beingadjusted to block out the notch 126 under such conditions.)

Initially, the various parts are in the neutral positions shown in FIG. 3 of the drawings. L1 order to make up the threaded joint 22, the control lever is pushed toward the hand grip 106, which can be accomplished conveniently by respectively gripping the control lever 160 and the hand grip 106 with the thumb and fingers of the right hand. This displaces the various parts into the operating positions shown in FIG. 4 of the drawings to produce clockwise rotation of the rotor 56. It will be understood that the speed of clockwise rotor rotation may be varied by varying the extent to which the control lever 100 is displaced toward the hand grip 106, thereby varying the extent of angular displacement of the control arm 94 from neutral, and correspondingly varying the extent of movement of the motor actuating valve 70 toward its fully open position for clockwise rotor rotation. As shown in FIG. 4 of the drawings, the latch means 110 is inoperative under such conditions, entry of the pawl 124 into the notch 128 being prevented by the selector element 130. Also, under such conditions, the push-rod spring 152 maintains the push rod 148 in its radially outward position to prevent engagement of the cam 154 on the rotor 56 with the inner end of the push rod every time the rotor completes one revolution.

After the threaded joint 22 has been fully made up in the foregoing manner, the operator releases the control lever 100, whereupon the various parts are restored to the positions of FIG. 3 by the biasing means incorporated in the motor actuating valve 70. If it is subsequently desired to align or register the throat 58 in the rotor 56 with the throat 52 in the housing 50 to permit disengagement of the power wrench 32 from the drill string 24, it is merely necessary for the operator to displace the control lever 100 toward the hand grip 108 sufficiently to permit the pawl 124 to enter the open notch 126. This may be accomplished readily by grasping the control lever 100 and the hand grip 108 with the fingers and thumb, respectively, of the right hand. Initially, the control lever 100 may be squeezed hard enough to position the pawl 124 adjacent the right hand edge of the notch 126, as viewed in FIG. 5, thereby increasing the starting torque developed by the motor 64 in the counterclockwise direction to assist in overcoming starting friction. Subsequently, the control lever 100 is released, whereupon the parts occupy the positions shown in FIG. 5 of the drawings. It will be noted that the arm 144 connected to the pawl 124 has displaced the push rod 148 inwardly so that the inner end of the push rod is in a position to be engaged by the cam 154 on the rotor 56 as the throat 58 in the rotor approaches alignment with the throat 52 in the housing 50. It will be understood that the adjusting screws 118 are so set as to provide a counterclockwise rotor speed precisely equal to that necessary to cause the rotor to coast the exact amount necessary to achieve accurate throat alignment. Normally, this is a rather slow rotor speed.

Ultimately, as throat alignment is approached, the cam 154 on the rotor 56 engages the inner end of the push rod 148 to cause the push rod, acting through the arm 144, to disengage the pawl 124 from the notch 126 in the latch elements 114. This releases the latch means 110 to permit the centering means incorporated in the motor actuating valve 70 to restore the various parts to their neutral of FIG. 3 positions. This, of course, de-energizes the motor 64 and the rotor 56 coasts the angular amount necessary to achieve accurate registering of the throat 58 in the rotor with the throat 52 in the housing 50, whereupon the power wrench 32 may be disengaged from the drill string 24.

Although an exemplary embodiment of the invention has been disclosed herein for purposes of illustration, it will be understood that various changes, modifications and substitutions may be incorporated in such embodiment without departing from the spirit of the invention as defined by the claims which follow.

I claim as my invention:

1. A control system for a power wrench of the type which includes a housing, a jaw-carrying rotor mounted on and rotatable relative to said housing in opposite directions, a reversible motor carried by said housing and connected to said rotor for rotating said rotor in opposite directions, and motor actuating means on said housing and selectively movable from a neutral position into two operating positions for selectively energizing said motor for rotation in opposite directions, said motor actuating means being biased toward said neutral position, said control system including:

(a) manually-operable control means on said housing for selectively moving said motor actuating means from its neutral position into its operating positions;

(b) releasable latch means on said housing for selectively latching said motor actuating means in one of its operating positions to prevent it from returning to its neutral position;

(c) intereng-ageable means on said housing and said rotor for releasing said latch means as said rotor approaches a predetermined angular position relative to said housing; and

(d) whereupon said motor actuating means returns to its neutral position to de-energize said motor.

2. A power-wrench control system according to claim 1 wherein said latch means includes:

(a) a first latch element;

(b) a second latch element having two engagement means selectively engageable by said first latch element to latch said motor actuating means in its respective operating positions; and

(c) selector means for selectively preventing engagement of said first latch element with one of said engagement means.

3. A power-wrench control system as defined in claim 2 wherein:

(a) said control means includes a control shaft mounted on said housing for selective pivotal movement from a neutral position into two operating positions respectively corresponding to the neutral position and the two operating positions of said motor actuating means;

(b) said motor actuating means is connected to said control shaft;

(c) said first latch element is connected to said interengageable means; and ((1) said second latch element is mounted on and connected to said control shaft. 4. A power-wrench control system as set forth in claim 3 including means for angularly adjusting said second latch element relative to said control shaft to adjust the speed of said motor when said motor actuating means is latched in either of its operating positions.

5. A power-wrench control system according to claim 4 wherein:

(a) said engagement means comprise notches in said second latch element enterable by said first latch element; and

(b) said selector means comprises means for selectively closing one of said notches to prevent entry by said first latch element.

6. A power-wrench control system according to claim 1 including means for adjusting the speed of said motor when said motor actuating means is latched in one of its operating positions.

7. A power-wrench control system as defined is claim 1 wherein said interengageable means includes:

(a) a cam on said rotor; and

(b) means on said housing and engageable by said cam for releasing said latch means as said rotor approaches said predetermined angular position relative to said housing.

8. A power-wrench control system according to claim 1 wherein:

(a) said reversible motor is a reversible fluid motor; and

(b) said motor actuating means includes valve means for selectively energizing said motor for rotation in opposite directions.

9. A power-wrench control system as defined in claim 1 wherein:

(a) said housing and said rotor are provided with registrable radial throats for lateral insertion and withdrawal of a pipe, or the like; and

(b) said throats are in register when said rotor is in said predetermined angular position relative to said housing.

10. A power-Wrench control system as set forth in claim 4 1 wherein:

(a) said housing is provided with two generally parallel hand grips; and (b) said control means includes a control lever between and generally parallel to said hand grips.

References Cited UNITED STATES PATENTS 2,618,468 11/1952 Lundeen 81-57.1 2,703,221 3/1955 Gardner 81-5113 2,846,909 8/1958 Mason 81 57.1X 3,180,186 4/1965 Catland 8157.1

JAMES L. JONES, JR., Primary Examiner. 

